Traditional methods of removing impurities in water include the use of activated carbon filters. One common type of activated carbon filter is known as a “carbon block filter”. Carbon block filters have activated carbon particles held together by a thermoplastic binder and are typically molded or extruded to form a shaped block (for example, a hollow cylinder or a disk).
The use of chloramine instead of chlorine as a disinfectant for municipal water treatment is becoming more common in the United States and other countries. In general, chloramine imparts a bad taste to water making its removal desirable for some applications (for example, drinking water).
Removal of chloramine with activated carbon is substantially more difficult than removal of chlorine. Because of the difficulty in removing chloramine, activated carbon manufacturers (for example, MeadWestvaco and Calgon Carbon) have developed carbons known in the art as “catalytic activated carbon” with enhanced catalytic activity for removal of chloramine as compared to traditional activated carbons. Even with such carbons, substantially more contact time is required for chloramine removal than most other chemical contaminants found in municipal water.
As a result, state-of-the-art filters for chloramine removal are generally large and are often designed for removal of chloramine only. Such filters have application to commercial water filtration, for example, food service applications, but are poorly suited for residential use where filters desirably have a relatively small physical size and remove multiple contaminants.